1. Field
The present art relates to a multilayer interconnection substrate and a manufacturing method therefor, and in particular, to a multilayer interconnection substrate including different types of substrate layers, and a manufacturing method therefor.
2. Description of the Related Art
Conventionally, multilayer interconnection substrates having a plurality of interconnection layers are used commonly as interconnection substrates for increasing a density. Further, as multilayer interconnection substrates, ceramic multilayer interconnection substrates using a ceramic as an insulating material on which an interconnection layer is formed, and resin multilayer interconnection substrates using a resin as an insulating material, are used commonly.
The ceramic multilayer interconnection substrates are advantageous since the number of laminated layers can be increased and they have a low thermal expansion coefficient. However, they are not suitable for minute interconnection. Therefore, when interconnection is to have an increased density, it is necessary to increase the number of laminated layers, and thus, a product cost increases accordingly.
On the other hand, the resin multilayer interconnection substrates are not expensive, minute interconnection is allowed, and also, it is possible to increase the number of layers. However, a thermal expansion coefficient is high, and thereby, mounting reliability for when electronic devices such as semiconductor devices are mounted is low.
Therefore, as being discussed in Japanese Laid-Open Patent Application 55-11883, a multilayer interconnection substrate in which ceramic are placed on both sides of a resin multilayer interconnection substrate is proposed.
However, in the multilayer interconnection substrate discussed in Japanese Laid-Open Patent Application 55-11883, the ceramic does not have interconnection, and is used merely as a reinforcement material. Therefore, interconnection is provided entirely in the resin multilayer interconnection substrate, and thus, freedom in interconnection design is low.
Further, the ceramic functioning as the reinforcement martial is provided only on both sides, i.e., obverse and reverse sides of the resin multilayer interconnection substrate. Therefore, a stress caused by thermal expansion of the resin multilayer interconnection substrate cannot be sufficiently eased only by the ceramic provided only on both sides, i.e., obverse and reverse sides of the resin multilayer interconnection substrate. Therefore, it is not possible to sufficiently increase mounting reliability even when the ceramic is thus used.